In this chapter, we elaborate on the topic of European integration in science. We will not deal with questions related to the effects of European integration, but only with the scientometric question how one can quantitatively indicate integration of the European science system. Our study is intended to facilitate and supplement debates rather than to provide a final answer to the questions whether European integration 'exists'. In this chapter, we first discuss the use of scientometric indicators in research evaluation from a historical perspective in (section 2). A discussion of European science policy follows (section 3). Then, we introduce a number of indicators of integration and discuss our empirical results concerning the evolution of the European science system in the 1980s and 1990s (section 4). We close the chapter with a discussion of possible avenues of future research for enhancing research evaluation (section 5).